Continuous coil pretreatment process
Described herein is a continuous coil pretreatment process used to treat the surface of an aluminum alloy sheet or coil for subsequent deposition of an acidic organophosphorus compound. The process can include applying a cleaner to a surface of an aluminum sheet or a coil; etching the surface of the aluminum sheet or the coil with an acidic solution; rinsing the surface of the aluminum sheet or the coil with deionized water; applying to the surface of the aluminum sheet or the coil a solution of an acidic organophosphorus compound; rinsing the surface of the aluminum sheet or the coil with deionized water; and drying the surface of the aluminum sheet or the coil.
1. A continuous coil pretreatment process comprising:
a) cleaning a surface of an aluminum sheet or a coil; then
b) etching the surface of the aluminum sheet or the coil by spraying the surface of the aluminum sheet or the coil with an acidic etching solution comprising up to about 8 vol. % of sulfuric acid for a period of from about 5 seconds to about 15 seconds, wherein the acidic etching solution in contact with the surface of the aluminum sheet or the coil is controlled by replacing or replenishing the acidic etching solution when a combined concentration of aluminum and magnesium ions exceeds 1,000 ppm; then
c) rinsing the surface of the aluminum sheet or the coil with deionized water; then
d) applying to the surface of the aluminum sheet or the coil a solution comprising a vinylphosphonic acid-acrylic acid (VPA-AA) copolymer; then
e) rinsing the surface of the aluminum sheet or the coil by (i) spraying the surface of the aluminum sheet or the coil with deionized water in a spray direction opposite a feed direction of the aluminum sheet or the coil as it advances in the continuous coil pretreatment process, (ii) providing a water dam at an entry point of an exit squeegee roll, and (iii) continuously rinsing a surface of the exit squeegee roll; and then
f) drying the surface of the aluminum sheet or the coil.
2. The process of claim 1 , wherein a concentration of the vinylphosphonic acid-acrylic acid (VPA-AA) copolymer in the solution comprising the vinylphosphonic acid-acrylic acid (VPA-AA) copolymer is about 0.4 wt. % to about 10 wt. %.
3. The process of claim 1 , wherein a concentration of the vinylphosphonic acid-acrylic acid (VPA-AA) copolymer in the solution comprising the vinylphosphonic acid-acrylic acid (VPA-AA) copolymer is about 0.6 wt. % to about 5 wt. %.
4. The process of claim 1 , wherein a concentration of the vinylphosphonic acid-acrylic acid (VPA-AA) copolymer in the solution comprising the vinylphosphonic acid-acrylic acid (VPA-AA) copolymer is about 0.7 wt. % to about 3 wt. %.
5. The process of claim 1 , wherein a concentration of the vinylphosphonic acid-acrylic acid (VPA-AA) copolymer in the solution comprising the vinylphosphonic acid-acrylic acid (VPA-AA) copolymer is about 0.8 wt. % to about 1.0 wt. %.
6. The process of claim 1 , wherein the acidic etching solution further comprises hydrofluoric acid, nitric acid, phosphoric acid, or mixtures thereof.
7. The process of claim 1 , wherein the acidic etching solution further comprises hydrofluoric acid.
8. The process of claim 1 , wherein the deionized water in step (c) has a conductivity of less than or equal to 25 uS/cm.
9. The process of claim 1 , wherein the aluminum sheet or the coil is made from an aluminum alloy selected from the group consisting of 5XXX and 6XXX alloys.
10. The process of claim 1 , wherein the aluminum sheet or the coil is made from an aluminum alloy selected from the group consisting of AA5754, AA5182, AA6451, AA6111 and AA6014 alloys.
11. The process of claim 1 , wherein the cleaning in step (a) comprises applying a cleaner comprising water.
12. The process of claim 11 , wherein the cleaner further comprises an acid, an alkali, a surfactant, a detergent, or mixtures thereof.
13. The process of claim 1 , wherein the applying in step (d) is performed by immersing the aluminum sheet or the coil in the solution comprising the vinylphosphonic acid-acrylic acid (VPA-AA) copolymer.
14. The process of claim 1 , wherein the applying in step (d) is performed by spraying the aluminum sheet or the coil with the solution comprising the vinylphosphonic acid-acrylic acid (VPA-AA) copolymer.
15. The process of claim 1 , wherein the acidic etching solution in contact with the surface of the aluminum sheet or the coil in step (b) is controlled to maintain the combined concentration of aluminum and magnesium ions to a range from 800 ppm to less than 1,000 ppm.
16. A continuous coil pretreatment process comprising:
a) cleaning a surface of an aluminum sheet or a coil by water spray impingement; then
b) etching the surface of the aluminum sheet or the coil by spraying the surface of the aluminum sheet or the coil with an acidic etching solution comprising about 1.5 to about 10 vol. % of sulfuric acid for a period of about 5 seconds to about 15 seconds, wherein the acidic etching solution in contact with the surface of the aluminum sheet or the coil is controlled to maintain a concentration of aluminum and magnesium ions not exceeding 1,000 ppm and wherein the acidic etching solution is replaced or replenished when the concentration of aluminum and magnesium ions exceeds 1,000 ppm; then
c) rinsing the surface of the aluminum sheet or the coil with deionized water at a temperature of about 37° C. to about 65° C.; then
d) applying to the surface of the aluminum sheet or the coil a solution comprising a vinylphosphonic acid-acrylic acid (VPA-AA) copolymer for a period of about 5 seconds to about 20 seconds, wherein a concentration of the vinylphosphonic acid-acrylic acid (VPA-AA) in the solution comprising the vinylphosphonic acid-acrylic acid (VPA-AA) copolymer is about 0.8 wt. % to 1.0 wt. %; then
e) rinsing the surface of the aluminum sheet or the coil either immediately after step (d) or with a delay of about 1 second to about 5 seconds, wherein the rinsing comprises (i) spraying the surface of the aluminum sheet or the coil with deionized water in a spray direction opposite a feed direction of the aluminum sheet or the coil as it advances in the continuous coil pretreatment process, (ii) providing a water dam at an entry point of an exit squeegee roll, and (iii) continuously rinsing a surface of the exit squeegee roll; and then
f) drying the surface of the aluminum sheet or the coil.
17. The process of claim 16 , wherein the acidic etching solution is combined with a surfactant additive or an accelerator.
18. The process of claim 16 , wherein the acidic etching solution in contact with the surface of the aluminum sheet or the coil in step (b) is controlled to maintain the concentration of aluminum and magnesium ions to a range from 800 ppm to less than 1,000 ppm.
19. The process of claim 16 , wherein the acidic etching solution in contact with the surface of the aluminum sheet or the coil in step (b) comprises about 1.5 to about 8 vol. % of sulfuric acid.